340 INTRODUCTION TO CONCHOLOGY. 



altogether wanting. The muscular impression has a large 

 sinus. 



The characteristic genus Corhis, instituted by Cnvier^ 

 displays a beautiful shelly which is easily recognized by lon- 

 gitudinal and transverse fimbriated undulations, or lamellar 

 ridges, crossing the external surface of the valves, and 

 diverging, also, from the umboes to the margin. The 

 colour is uniformly of a clear white, occasionally tinged 

 or radiated with pink. 



The genus Luchia comprehends a natural assemblage of 

 species, selected from the Tellince and Veneres of Linnseus : 

 they exhibit a peculiar similarity of form, but are remark- 

 able for the variety of character displayed on the surface 

 of the interior. The hinge and teeth are irregular in their 

 development ; it is, therefore, needful to mention that the 

 shell is generally orbicular, equivalve, inequilateral, some- 

 what depressed; that the umboes are small, acute, and 

 oblique, and that the hinge has sometimes two divergent 

 teeth, sometimes none ; lastly, that one valve contains two 

 lateral teeth, one on either side, the anterior situated near 

 the hinge, while in the other there is but one ; the teeth 

 are, however, often obsolete. The muscular impressions of 

 attachment are distant from each other : the anterior forms 



